This circuit was found in the July 1988 issue of Radio Electronics magazine. It makes use of an operational transconductance amplifier (OTA) still in use today.
This circuit was obtained in a 1973s documentation. The transistors may be BC558 for the PNP and...
The sensors in this circuit that triggers when the temperature goes out of a certain range are...
Other operational amplifiers series, such as MC34072, MC34074, MC35071, MC35072, MC35074 d MC33071...